fix(package): update webpack to version 2.3.1
fix(package): update webpack to version 2.3.1

https://greenkeeper.io/

syuilo/Misskey,armchair-philosophy/misskey,Tosuke/misskey,armchair-philosophy/misskey,armchair-philosophy/misskey,ha-dai/Misskey,Tosuke/misskey,Tosuke/misskey,ha-dai/Misskey,syuilo/Misskey,Tosuke/misskey,armchair-philosophy/misskey,Tosuke/misskey